Many polymer compositions are packaged in flexible packages such as paper and plastic bags. The bags are generally sealed at one end, placed under the exit orifice of a polymer manufacturing line, filled with polymer and sealed. Sealing means used include thread (e.g., cotton), various adhesives and, in the case of plastic bags, heat sealing.
In the case where the polymer compositions are to be melt processed or masticated at high temperature, it has been desirable to package the melt processible polymer in a bag made from a plastic that, when processed along with the polymer composition, does not adversely affect the desired properties of the polymer composition. The advantages of such a combination are that the bag and polymer contents can be added to the processor together without having to open and empty the bag; and, of course, there are no empty bags to dispose of. The sealing means for such plastic bags have varied, the most common being heat sealing. Heat sealing is, however, not useful in situations where the polymer composition to be packaged is heat-sensitive, or where the polymer composition to be packaged contains powdery fines, or talc (hereinafter a heat seal sensitive polymer). For example, neoprene, a well-known homopolymer of chloroprene, or copolymer of chloroprene with other unsaturated monomers, is sold as unvulcanized chips that are quite tacky. To reduce the tackiness for ease of handling, the surface of chips is treated with the talc. The talc, however, interferes with heat-sealing processes. One way to overcome this problem is disclosed in U.S. Pat. No. 4,190,156 (Adam) whereby a thermoplastic bag is closed using synthetic polymer thread. The bag material and thread are said to be readily dispersible in the neoprene at the blending temperature to give homogeneous dispersion. The thread used is made from polyvinyl alcohol having a melt temperature of 213.degree. (well above the processing/compounding temperature of neoprene, i.e, 100.degree.-120.degree. C.) and is said to have sufficiently low strength so as to break and disperse readily in the polymer at the blending stage. However, in some applications, dispersed particulate polymer such as polyvinyl alcohol is undesirable in that it interferes with the processing of the polymer.
Therefore, there remains a need for a bag/seal packaging system, for heat-seal sensitive polymers, where the bag/seal can be introduced into the polymer melt processor unopened, and where the bag/seal composition will not interfere with the processing of the polymer.